Uncured unsaturated polyester composition

ABSTRACT

An uncured unsaturated polyester resin composition useful in the production of molded articles of cured unsaturated polyester resins, the composition comprising (1) 60 to 97% by weight of an uncured unsaturated polyester resin which is a liquid mixture of at least one unsaturated polyester and at least one unsaturated monomer for curing the polyester, and (2) 40 to 3% by weight of a modifying polymer of the microgel structure which is obtained by polymerizing 97 to 30% by weight of at least one radical polymerizable monomer in the presence of 3 to 70% by weight of at least one rubbery polymer having double bonds in the molecule, is finely dispersible, without dissolving, in both of said unsaturated polyester resin and said unsaturated monomer for curing the polyester, and contains 0.1 to 10% by weight of carboxyl groups in the molecule.

United States Patent n 1 Hara et al.

[451 Apr. 29, 1975 1 UNCURED UNSATURATED POLYESTER COMPOSITION [73] Assignee: Kuraray Co., Ltd., Kurashiki,

Okayama Prefecture Japan [22] Filed: May 11,1973

{21} Appl. No.: 359,426

3.733 370 5/1973 Thompson et al. 260/862 3.772.241 11/1973 Kroekel 260/40 R Primary Examiner-Melvin Goldstein ASS/Stan! Examiner-E. A. Nielsen Attorney, Agent, or FirmSherman & Shalloway ABSTRACT An uncured unsaturated polyester resin composition useful in the production of molded articles of cured unsaturated polyester resins, the composition comprising (1) 60 to 97% by weight of an uncured unsaturated polyester resin which is a liquid mixture of at least one unsaturated polyester and at least one unsaturated monomer for curing the polyester, and (2) 40 to 3% by weight of a modifying polymer of the microgel structure which is obtained by polymerizing 97 to 30% by weight of at least one radical polymerizable monomer in the presence of 3 to 70% by weight of at least one rubbery polymer having double bonds in the molecule, is finely dispersible, without dissolving, in both of said unsaturated polyester resin and said unsaturated monomer for curing the polyester, and contains 0.1 to 10% by weight of carboxyl groups in the molecule.

5 Claims, No Drawings UNCURED UNSATU RATED POLYESTER COMPOSITION This invention relates to an uncured unsaturated polyester resin composition which is useful in the production of shaped articles of cured unsaturated polyester resm.

As is well known, the uncured unsaturated polyester resin is a viscous liquid mixture having flowability which is obtained by dissolving at least one uncured unsaturated polyester (which is often called an unsaturated alkyd) in at least one unsaturated monomer for curing the polyester, for example, styrene [t is a resinous material for the preparation of cured unsaturated polyester resins which has not undergone a curing treatment.

Techniques for producing cured unsaturated polyester resins by subjecting to a curing and shaping treatment an uncured unsaturated polyester resin which contains or does not contain a reinforcing material such as glassfibers have been known for many years, and the resulting shaped articles have found a wide range of applications because of their superior properties and feasibility. However, the uncured unsaturated polyester resin has the defect of undergoing high shrinkage during curing, and therefore, cured shaped articles obtained by press molding or injection molding such a polyester resin using a mold contain strains or cracks and also suffer from various disadvantages such as the occurrence of sink marks, the lack ofsmoothness of the surfaces of the articles or the projection of the glassfibers incorporated onto the surfaces of the articles. In an attempt to overcome these disadvantages, there has recently been proposed a method in which a thermoplastic resin such as polystyrene, or poly(methyl methacrylate) is incorporated in an uncured unsaturated polyester resin in order to improve its shrinkage property, and then the mixture is cured. This method can give a shaped article substantially free from shrinkage caused by curing, and the above-mentioned diffi culties have been overcome to a great extent.

In recent years, techniques for providing prepreg mats, sheet molding compounds (SMC) and bulk molding compounds (BMC) useful as materials for preparing reinforced cured shaped articles by press molding or injection molding have been developed. These techniques are based on the utilization of a viscosity increasing phenomenon which will occur when a small amount of a thickner such as magnesium oxide or calcium hydroxide is incorporated in an uncured unsaturated polyester resin, and involves incroporating the thickner, reinforcing fibers, a filler, a curing catalyst, and other additives if desired, in an uncured unsaturated polyester resin, The commercial importance of these techniques has very much increased. In these prepreg mats, SMC or BMC, the uncured unsaturated polyester resin is transformed to a soft solid mass devoid of stickiness owing the action of the thickner, and therefore lends itself to far easier handling and molding operation than ordinary uncured unsaturated polyester resins which are liquid and highly tacky and contain no thickner. Furthermore, such an uncured unsaturated polyester resin composition can be uniformly molded together with the reinforcing fibers. These uncured thickner-incorporated unsaturated polyester resin compositions are rarely cured and molded immediately after their preparation, but generally stored for several months at most before being put to use for preparing the desired cured articles.

The uncured unsaturated polyester resin compositions containing a thickner still have the property of being shrunk at the time of curing which property is possessed inherently by the uncured unsaturated polyester resins. Accordingly, unless some modification of the uncured and unsaturated polyester resins is performed, the various troubles caused by the high shrinkage of the uncured unsaturated polyester resin, as mentioned above, cannot be obviated. These difficulties would be overcome ifa thickner and a reinforcing material are incorporated into an uncured unsaturated polyester resin composition containing a thermoplastic resin as a shrinkage-improving polymer to form a prepreg mat, SMC or BMC. However, the resulting composition suffers from the low dispersion stability of the shrinkage-improving polymer in the composition during its storage for long periods of time. This defect of low dispersion stability, or the poor storage stability of the composition, means that the dispersed state of the shrinkage-improving polymer in the thickened composition becomes poor during the storage of the prepreg mat, SMC or BMC. In other words, it means that a solution of the shrinkage-improving polymer in a crosslinking monomer (for example, styrene) present in the composition agglomerates to form coarse particles. or exudes onto the surface of the prepreg, SMC or BMC, If such a prepreg mat, SMC or BMC is molded using a mold, the shrinkage-improving polymer adheres to the surface of the mold, and the surface of the cured molded product has poor luster and smoothness and at times, suffers from colored spots. Furthermore, since the surface of such a prepreg mat, SMC or BMC becomes tacky, the working efficiency is reduced. The problem of dispersion stability of the composition containing a thickner does not matter much in the case of the composition containing no thickner There has been proposed a method in an attempt to reduce the shrinkage of the thickened composition and overcome the problem of poor dispersion stability, which method involves the use of, as the shrinkageimproving polymer, a carboxyl-containing thermoplastic resin (such as a copolymer of methyl methacrylate and acrylic acid) which is soluble either in a crosslinking monomer such as styrene or an uncured unsaturated polyester resin. This method has contributed to some extent to the improvement of the dispersion stability and the prevention of shrinkage at the time of molding, but has not proved entirely satisfactory. Especially, this method cannot give a cured molded article having satisfactory surface smoothness.

It is an object of this invention to provide an uncured unsaturated resin composition which is free from the above-mentioned defects of the conventional uncured unsaturated polyester resins and useful in the production of a cured unsaturated polyester resin molded article.

According to the present invention, there is provided a composition that can be used especially preferably as an uncured unsaturated polyester resin component in the preparation of a starting material for producing a reinforced cured unsaturated polyester resin molded article, which comprises the uncured unsaturated polyester resin, a thickner and reinforcing fibers, such as a prepeg mat, SMC or BMC. By using the composition of this invention as the uncured unsaturated polyester resin component. there can be produced a prepreg mat. SMC or BMC capable of giving a smooth lustrous reinforced cured article. which has good storage stability, reduced shrinkage during curing. and no tendency to the adhesion to the mold. and does not cause sink marks at the rib and boss portions of the mold.

One type of the uncured unsaturated polyester resin composition in accordance with this invention comprises (l) 60 to 97 by weight of an uncured unsaturated polyester resin which is a liquid mixture of at least one unsaturated polyester and at least one unsaturated monomer for curing the polyester. and (2) 40 to 3 by weight of a modifying polymer of microgel structure which is obtained by polymerizing 97 to 30 70 by weight of at least one radial polymerizable monomer in the presence of 3 to 70 by weight of at least one rubbery polymer having double bonds in the molecule, is finely dispersible. without dissolving, in both of said unsatu rated polyester resin and an unsaturated monomer for curing the polyester, and contains 0.1 to 10 by weight of carboxyl groups in the molecule.

Another type of the uncured unsaturated polyester resin composition in accordance with this invention comprises l) 60 to 97 by weight of an unsaturated polyester resin which is a liquid mixture of at least one unsaturated polyester and at least one unsaturated monomer for curing the polyester, and (2} 40 to 3 by weight of a combined modifying polymer component which comprises (a) 80 to 5 by weight of a polymer of microgel structure which is obtained by polymerizing 97 to 30 by weight of at least one radical polymerizable monomer in the presence of 3 to 70 by weight of at least one rubbery polymer having double bonds in the molecule, and is finely dispersible. without dissolving. in both of said unsaturated polyes ter resin and an unsaturated monomer for curing the polyester, and (b) 20 to 95 by weight of at least one thermoplastic polymer soluble in at least one of said unsaturated polyester resin and unsaturated monomer for curing the polyester. at least one of the polymers (a) and (b) containing carboxyl groups in the molecule. the total amount of said cafboxyl groups being 0.1 to by weight based on the total weight of the polymers (a) and (b).

The above compositions in accordance with this in vention contribute to the effective achievement of the object of this invention. The second type is more preferred for various advantages to be described hereinafter.

The modifying polymers of microgel structure which constitute component (2) are important ingredients the present invention. The other components. that is. the unsaturated polyesters. unsaturated monomers for curing the polyester and the uncured unsaturated polyester resins each of which is a liquid mixture of at least one unsaturated polyester and at least one unsaturated monomer for curing the polyester and the polymers sol uble in the uncured unsaturated polyester resins have been known previously. Also. the thickener, reinforcing fibers. filler. curing catalyst. and other additives have previously been known. All of these known components and additives can be used in the present inven' tion. It is to be understood therefore that the descrip tion of these known components and additives in the present specification is for the purpose of illustration only. and does not in any way limit the present inventlon.

The unsaturated polyester is produced by a known method such as the melting method. the solution method or the epoxy method using an afimnsaturated dibasic acid and a glycol together. if desired, with an aromatic saturated dibasic acid or an aliphatic saturated dibasic acid. Examples of the afimnsaturated dibasic acid are maleic anhydride. maleic acid. fumaric acid. mesaconic acid. tetraconic acid. itaconic acid. chlorinated maleic acid, and dimethyl esters of these acids. Examples of the glycol are ethylene glycol. diethylene glycol. propylene glycol. dipropylene glycol, bu tylene glycol. neopentyl glycol. hexylene glycol. hydrogenated bisphenol A. 2.2'-di(4-hydroxypropoxyphenol) propane, and 2.2'-di(4-hydroxyethoxyphenyl) propane. In addition to these glycols. ethylene oxide and propylene oxide are also useful.

The aromatic saturated dibasic acid may. for example, be phthalic acid, phthalic anhydride. isophthalic acid. terephthalic acid, tetrahydrophthalic acid. halogenated phthalic anhydride. and dimethyl esters of these acids. The acid component contains the afiunsaturated dibasic acid in an amount of 50 to 100 mol%. If the amount is less than 50 mol%. the effect of reduc ing the shrinkage is not satisfactory.

The unsaturated polyester preferably has a molecular weight in the range of L000 to 3.000. an acid value of 5 to 50 and a hydroxyl value of 5 to 60.

The crosslinking unsaturated monomer to be used in admixture with the unsaturated polyester may be any monomer having radical polymerizability with the unsaturated polyester. Examples include styrene. vinyl toluene. chlorostyrene. divinyl benzene. t-butyl styrene. vinyl acetate, diallyl phthalate. acrylic acid esters. and methacrylic acid esters. Of these. the styrene type unsaturated monomers are preferred. The mixing proportions of the unsaturated polyester and the crosslinking unsaturated monomer are 30 to 80 by weight for the former and 20 to by weight for the latter. The resulting mixture is a liquid and is generally called an uncured unsaturated polyester resin.

Usually known thickeners for the uncured unsaturated polyester resin include oxides or hydroxides of alkaline earth metals such as magnesium oxide. magnesium hydroxide or calcium hydroxide (together with calcium oxide. if desired). The amount of the thickner is suitably 0.2 to l0 parts by weight per [00 parts by weight of a mixture of the uncured unsaturated polyester resin and the shrinkage-improving polymer.

The polymeric material of the microgel structure which contains a carboxyl group in the molecule is present as very stable finely dispersed particles in the uncured unsaturated polyester resin composition. Accordingly. the polymeric material does not agglomerate. nor exudes onto the surface of the composition during storage. Furthermore. because of the microgel structure. this polymeric substance does not melt by heating. Accordingly. no phase separation of the poly mer occurs as a result of the melt-adhesion of the dispersed particles of the polymer to each other at the time of curing and molding the composition containing this polymer. Thus. by curing and molding the comp0- sition in a mold. a sufficient effect of reducing the shrinkage of the uncured unsaturated polyester resin is exhibited. and there can be obtained a smooth and his trous cured shaped article free from defects such as cracks. sink marks or projections of the reinforcing fibers.

A mixture of the polymeric material having a microgel structure and the unsaturated polyester resin has a considerably high viscosity, and a composition consisting of this mixture and a filler such as calcium carbonate has a higher viscosity. This may lead to insufficient impregnation of the composition into the reinforcing fibers when producing a prepreg mat or SMC containing a relatively large amount of a filler, and sometimes, a satisfactory cured shaped article cannot be obtained. If a combined modifying polymer consisting of the polymer of microgel structure and a soluble polymer to be described below is added to the uncured unsaturated polyester resin as in the composition of the sec ond type, the impregnation of the composition into the reinforcing fibers is improved, and the abovementioned difficulty can be overcome. it is essential that one or both of the polymer of the microgel structure and the soluble polymer should contain a carboxyl group. Such an effect is exhibited when the polymer of the microgel structure and the soluble polymer are used conjointly. When the soluble polymer alone is mixed with the unsaturated polyester resin, the viscosity of the mixture can be rendered relatively low and the impregnatability of the mixture into the reinforcing fibers. However. the effect of reducing the shrinkage is poor, and the dispersion stability of the soluble polymer in SMC or BMC is insufficient. Accordingly, the dispersed particles agglomerate into a large mass during storage. and causes a macroscopic phase separation. Such a mass adheres to a mold during shaping to cause the loss of luster of the molded article. It is difficult therefore to obtain a prepreg mat, SMC or BMC of low shrinkage.

The polymer of the microgel structure used in this invention can be formed by polymerizing 97 to by weight of at least one radical polymerizable monomer in the presence of 3 to 70 by weight of at least one rubbery substance having double bonds in the molecule, for example according to the emulsion polymerization or the suspension polymerization. In order to obtain a microgel polymer containing a carboxyl group, either one or both of the rubbery substance and the polymerizable monomer used in the above-mentioned polymerization process should contain a carboxyl group. Because of the presence of the rubbery substance, this polymer is structurally heterogeneous, and often contains a slight degree of crosslinking structure, and therefore, it can be dispersed in the unsaturated polyester resin and the crosslinking monomer as fine particles without dissolving.

The rubbery polymer used for the production of the microgel polymer may be any rubbery polymer having double bonds on the main chain and/or side chains of the molecule. Such a rubbery polymer includes rubbery polymers of the butadiene, isoprene, chloroprene and acrylic ester types and an ethylene/propylene/nonconjugated diene rubber. Specific examples are polybutadiene, a butadiene/styrene copolymer, a butadiene/acrylonitrile copolymer, a butadiene/an acrylic ester copolymer, a butadiene/a methacrylic ester copolymer, a butadiene/acrylic acid copolymer, a

polymer, and an ethylene/propylene/norbornene terpolymer.

The monomer to be polymerized in the presence of the rubber polymer for preparing a polymer of the microgel structure may be any radical polymerizable monomer. However, the modifying polymer component or the combined modifying polymer component should contain a carboxyl group in an amount of preferably 0.l to l0 by weight. Accordingly, according to the presence or absence of a carboxyl group in the rubbery polymer or its content, a radical polymerizable monomer which contains or does not contain a carboxyl group is properly chosen. Examples of the radical polymerizable monomer containing no carboxyl group are acrylic esters such as methyl acrylate, ethyl acry late, butyl acrylate or hexyl acrylate, methacrylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate or hexyl methacrylate, vinyl esters such as vinyl acetate or vinyl propionate, aromatic vinyl compounds such as styrene, a-methylstyrene or orthovinyl toluene, oe-olefins, diolefins, vinyl chloride, vinylidene chloride, and acrylonitrile. If desired, it is possible to use conjointly a bifunctional or higher polymerizable monomer such as divinyl benzene or triallyl cyanurate. Of these, the methacrylic esters and the aromatic vinyl compounds are especially preferred.

Examples of the radical polymerizable monomer containing a carboxyl group are acrylic acid, methacrylic acid, crotonic acid, maleic acid, monomethyl maleate, monobutyl maleate, fumaric acid, itaconic acid, and p-vinyl benzoic acid, which are a,B-unsaturated carboxylic acids.

The most preferred polymers of the microgel structure for use in the present invention are those obtained by copolymerizing a,B-unsaturated carboxylic acids with at least one of styrene, methyl methacrylate and acrylonitrile in the presence of polybutadiene or polyisoprene.

It has previously been known that the component (b), that is, the thermoplastic polymer soluble in the uncured unsaturated polyester resin and/or the unsaturated monomer for curing the polyester, which is used in the second type composition is used alone as a modifying polymer. Examples of such a thermoplastic polymer are those obtained by polymerizing or copolymerizing polymerizable monomers selected from the group consisting of aromatic vinyls such as styrene, acrylic esters, methacrylic esters, a-olefins, diolefins, vinyl esters such as vinyl acetate, vinyl chloride, vinylidene chloride acryl nitrile and methacrylonitrile; cellulose derivatives; and saturated polyesters. These polymers have a molecular weight of 1,500 to 10,000,000. Where a carboxyl-containing soluble polymer is desired, the introduction of a carboxyl group can be performed by various chemical reactions such as graft polymerization after the formation of the polymer. However, most suitably, a carboxylcontaining monomer is incorporated and copolymerized at the time of forming the polymer.

The soluble polymer can also be formed as a byproduct in the production of the polymer of the microgel structure by controlling the polymerization conditions properly. According to this method, a mixture of the microgel polymer and the soluble polymer can be obtained. The use of a rubbery substance containing no crosslinkage or containing only a slight degree of crosslinkage and the use of a polymerization regulating agent in a relatively large amount are the effective means of achieving this end.

Desirably, the mixing proportions of component (a) (microgel polymer) and component (b) (soluble polymer) in the combined modifying polymer are 80-5 by weight. and 20-95 by weight, respectively.

The weight ratio of the unsaturated polyester resin to the modifying polymer or the combined modifying polymer in the composition of this invention is 60:40 to 9713, preferably 75:25 to 95:5. If the ratio of the modifying polymer or the combined modifying polymer is lower than this specified range. the effect of reducing the shrinkage is not sufficient, and if it is higher than this range, the properties of the cured product, such as strength or hardness, are deteriorated.

In order to form the composition of this invention, the modifying polymer or the combined modifying polymer component can be admixed with the uncured unsaturated polyester resin, either as such or as a dispersion or solution in an unsaturated monomer for curing the unsaturated polyester. When the soluble polymer is added, it is especially preferred to add it in the form dissolved in the monomer for curing the unsaturated polyester. The monomer used to dissolve or disperse the modifying polymer component is the same as the monomer contained in the unsaturated polyester to cure it or a monomer copolymerizable with it. The amount of this monomer is determined as the monomer contained in the unsaturated polyester resin for curing It has been found that when a polymer containing a polar group inaddition to the carboxyl group is used as the modifying polymer or the combined modifying polymer is used, the fmal cured product obtained has improved adhesion to a coating composition to be applied to the surface of the cured article. Examples of such a polar group are OH, -COOR, -CONH, CN, and halogens. Where a combined modifying polymer consisting of the microgel polymer and the soluble polymer is used, at least one of them should contain the above-mentioned polar group. The preparation of such a modifying polymer may be effected by polymerizing the monomer in the presence of a polymerizable monomer containing the polar group. Examples of such a polymerizable monomer are acrylic esters, methacrylic esters, vinyl esters, acrylamides, vinyl chloride, vinylidene chloride, acrylonitrile, and methacrylonitrile.

A prepreg mat, SMC or BMC of superior quality can be prepared by incorporating a filler, a curing catalyst, a mold releasing agent, a coloring agent. an ultraviolet absorbent, or other additives into the resin composition of this invention before its viscosity becomes high as a result of mixing a thickner therewith, and impregnating the blend into a reinforcing fibrous mat or fibrous laminate, or mixing it with reinforcing fibers of short cut lengths. Generally, the reinforcing fibers are glass fibers, but polyvinyl alcohol fibers, carbon fibers, etc. can also be used. Useful fillers are calcium carbonate, barium sulfate, and kaolin, and the amount of the filler is 50 to 200 parts per parts of the unsaturated polyester resin composition. The curing catalyst is not a special one, and any conventional curing catalysts for premixes or prepreg mats can be used. Examples of the curing catalyst are dicumyl peroxide. t-butyl perbenzoate, di-t-butyl hydroperoxide, t-butyl peroctate, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane. and 2,5-

dimethyl hexyl-2,5-di-(peroxybenzoate). Stabilizers may be hydroquinone, p-benzoquinone, naphthoquinone, phenanthraquinone, t butyl catechol and mono-tbutyl hydroquinone. Other additives such as a coloring agent, a mold releasing agent or an ultraviolet absorbent, may be those conventionally used for plastics.

The curing temperature for the composition of this invention is suitably to 180C. If the temperature is lower than it, the effect of reducing the shrinkage cannot be exhibited.

The invention will be described in greater detail by the following Examples in which all parts and percent ages are by weight unless otherwise specified. The various properties shown in the Examples were measured in accordance with the following methods.

l. Solubility of the Modifying Polymer 10 parts of a modifying polymer (for example, a polymer of the microgel structure) was well mixed with parts of a monomer for curing the polyester (for example, styrene). The mixture was subjected to centrifugal separation for 20 minutes at a speed of 7.000 revolutions per minute. Then, the mixture was examined for the presence of the insoluble part precipitated.

2. lmpregnatability of the Composition in Glass Fibers The state of impregnation was observed by the naked eye, and evaluated on a scale of good and poor".

3. Surface Smoothness of the Cured Molded Article The smoothness of the surface of the molded article was measured usinga microcorder. The furnace given are the microinches of the surface roughness determined by scanning I inch. Smaller figures show better surface smoothness. it was also evaluated on a scale of good, fair," poor" and inferior."

4. Stability of SMC An SMC which was stored at room temperature for a prescribed period after production was evaluated on the basis of the following standard.

Evaluation State of SMC Good No surface tackiness; the polymer does not exude onto the surface even when a modifying polymer is mixed Fair Surface slightly tacky; the modifying polymer exudes onto the surface to a slight extent Inferior Surface very tacky, the modifying polymer exudes onto the surface 3. Preparation of SMC Evaluation Number of the crosscuts removed A Sheet molding compound was p p in acct": Good 0 0 dance with the followin reci e.

t g P Fair 5 to 20 Inferior 20 to l()0 q Unsaturated polyester resin (UPl] 58 parts Microgel polymer (0-! or (02) l3 EXAMPLE 1 Styrene 30 Zinc slearate 4 1. Preparation of Unsaturated Polyester Resin agy P P A glass reaction vessel equipped with a stirrer. a gas g' fifgl iliggfi flow inlet, a condenser and a thermometer was charged g ag 3 opped stran as. fibers 95 with 1.? mols of malelc anhydrlde, 0.5 mol of phthallc (fiber length 2 l anhydride and 2.05 moles of propylene glycol. and they were reaced for 10 hours at 200C m a snieam of T The resulting sheet molding compound was stable trogen to orm an unsaturated polyester having an acid [5 during storage for 3 months The styrene Solution of value of 4 3. 70 parts of the unsaturated polyester was the polymer did not gXude on tht: Surface of the dissolved in 30 parts of styrene to form an unsaturated sheet molding compound and the Surface did not polyester resin (UPJ come tdcky Preparano" Mlcrogel F .0lymer After allowing the sheet molding compound to stand A glass Eamon vessFl equlpped a suffer, a for 10 days at room temperature, it was molded using momfiteb gas flow mlet E and a Condenser a matched metal die at molding temperature of 140C. charged with 17 parts, as SOlld content, of polybutadlunder a molding pressure of 200 kg/cmr The molded ene latex, 80 parts of methyl methacrylate and 3 parts product was free from Sink marks and had Superior of methacryllc acid. The mixture was diluted with 180 surface smoothness. The properties of the molded parts of water, and sodium dodecylbenzenesulfonate product were measured, and the results are shown in (emulsifier), lauryl mercaptan (polymerization regula- Table ml) and potassium pefsulfate (Catalyst) were f In order to show the superior properties of the com- Thse the above mammals f reacted for 6 hours position of this invention more clearly, Controls 1 to 5 a nitrogen atmosphere at 60 C. The produt was salted were performed in the Same way as in Example out, washed, and dried to form a polymer (04) of the Cept as noted below microgel structure having a carboxyl content of 1.7 This polymer was insoluble in a monomer, such as sty- Control l rene, vinyl toluene or methylmethacrylate, for curing 42 parts f m unsaturated polyester resin p unsaturated R W resml0 P of thls P was used instead of 12 parts of the microgel polymer mer (G- l) was mixed with 90 parts of styrene, and the 3- and 30 parts f yrene i Example 1 3 h mixture was subjected to centrifugal separation for 20 total amount f was 100 part minutes at a speed of 7,000 revolutions per minute. The proportion of the precipitated portion was 93 Control 2 This P y (G'l) was "either soluble in Poly(methyl methacrylate) was used instead of the A p y p y was also Produced y the 40 microgel polymer G-l in Example I, 3). same procedure as above using 20 parts, as solids content, ofa polybutadiene latex. 12 parts of methyl meth- Control 3 acrylate, 65 parts of styrene, 3 parts of acrylic acid, l80 A copolymer prepared f 9 pans f h l h- Paris of flxchanged Water, Part5 OfGAFACRE acrylate and 4 parts of acrylic acid was used instead of 610 (emulsifier based on alkyl polyethyleneoxyphos h i l polymer (3-1 i E m le I, (3). phate, product ofToho Kagaku Kabushiki Kaisha), and l .5 parts of potassium persulfate catalyst. This polymer Control 4 had a carboxyl content of l.9 The polymer (6- Polystyrene was used instead of the microgel polymer was not uniformly soluble in a monomer, such as sty- 3- i E l 1 3 rene, vinyl toluene, or methyl methacrylate, for curing the unsaturated polyester. 10 parts of the polymer G-2 Control 5 was mixed with 90 parts of styrene, and the mixture was Instead of the microgel polymer G-l in Example I, subjected to centrifugal separation for 20 minutes at a (3), a carboxyl-free polymer (G'-l) obtained by polyspeed of 7,000 revolutions per minute. The proportion merizing l7 parts, as solids content, of a polybutaiene 0f the precipitated portion was about 90 The (3-2 latex and 83 parts of methyl methacrylate in the same was not soluble in UP-l. way as in Example l, (2) was used.

Table l Runs Modifying Carhoxyl Solubility Stability Surface Adhesion Nos, Polymer content of of the of SMC smoothness of the modifying of the molded pumt modifying polymer in product l) Polymer styrene [\vtfii l l 0-] l.7 Insoluble Good Good I20 Good (dispersed finely) 2 6-2 l9 lnsoluhle Good Good lSO Fair (dis ersed Table 1- Continued Runs Modifying Carhoxyl Solubility Stability Surface Adhesion Nos. Polymer content of of the of SMC smoothness of the modifying of the molded paint modifying polymer in product l Polymer styrene (wt/7U Control i None Good Inferior 2300 Good Control 2 Polytmethyl 0 Soluble Inferior Poor 500 Fair methacr) late) (ontroi 3 Copolymer of 2.4 Soluble Fair Fair 380 Good 96 parts of methyl methacrylate and 4 parts of acrylic acid Control 4 Polystyrene 0 Soluble Inferior Poor 700 Inferior Control 5 (i'-l 0 lnsoluhle Fair Fair 200 Good (finely dispersed) The surface smoothness of the molded product obtained from SMC which had heen ullovted to stand for it! days after preparation.

EXAMPLE 2 Control 7 Polymethyl (methacrylate) was used intead of (LI in A bulk molding compound was produced in accor- Example 2 dance with the following receipe. C m 8 A copolymer prepared from 96 parts of methyl methacrylate and 4 parts of acrylic acid was used instead of G-l in Example 2.

Unsaturated polyester resin (UP-l 65 parts Micro el oi *mer (G-l or (Ci-2) l0 Styren e p y Control 9 Zinc stearate 4 30 3W1 perbenmue 1,5 Polystyrene was used lnstead of (3-1 in Example 2. p-Benzoquinone 0.02 Magnesium oxide [,2 Conn- 10 Calcium carbonate I (C /hoppfd strand glass fibers G'-l used in Control 5 was used instead of 6-1 in Exr inc 35 ample 2.

Table 2 Runs Modifying Stability Surface smoothness Adhesion Nos. polymer of BMC of the molded proof duct paint l 0-] Good Good I30 Good 2 G2 Good Good I30 Fair Control 6 None Good Inferior 2000 Good Control 7 Polymethyl Inferior Poor 450 Fair (methacrylate] Control 8 Copolymer Fair Fair 350 Good of 96 parts methyl methacrylate and 4 parts of acrylic acid Control 9 Polylnferior Poor 700 Inferior styrene Control 10 (i-l Fair Fair 200 Good l )The surface smoothness of a molded product obtained from BMC which had been allowed to stand for l0 days after preparation The resulting bulk molding compound (BMC) was EXAMPLES 3 TO 13 stable during storage for 3 months.

After the BMC was allowed to stand at room temperature for l0 days after preparation. it was injection molded at l40C. and injection pressure of l 10 ,0 Kg/cm? Controls 6 to l0 were performed in the same way as in Example 2 as noted below.

Control 6 36 parts of the unsaturated polyester resin (UP-l) was used instead of [0 parts of (3-1 and 25 parts of my rene in Example 2.

These Examples show the effect of adding various polymers of the microgel mixture to an unsaturated polyester resin.

1. Preparation of Unsaturated Polyester Resin An unsaturated polyester having an acid value of 38 was prepared in the same way as in Example 1 from L0 mol of maleic anhydride. and L05 mols of propylene glycol. and parts of the unsaturated polyester was mixed with 30 parts of styrene to produce an unsaturated polyester resin (UP-2).

2. Preparation of Sheet Molding Compound (SMC) A sheet molding compound (SMC) was prepared from in accordance with the following recipe, and molded in the same way as in Example I.

EXAMPLES 14 TO l8 These Examples will illustrate the effect of adding the microgel polymer to various unsaturated polyesters. 1. Preparation of Sheet Molding Compound (SMC) A sheet molding compound was prepared in accor- Unsammled Pfllyefiter "35in (UP-3) 5 parts dance with the following recipe Microgel polymer l2 styrene 23 Zinc Suzanne 4 Unsaturated lyect 64 t-Bulyl Perherzoate L5 Polymer G-i 5 er m P p'Benzoqutnone (H Svtrene 76 Calcium carbonate I Suzanne Magnesium oxide L3 v Chopped strand of glass fibers 9U gg ggl sgm g (fiber length 2 mches) Calcium carbonate I20 Magnesium oxide L5 3. Preparation of Microgel Polymer chlpped 8mm! of glass l5 fibers (fiber length l 90 Using the rubbery substances and polymertzable inch) monomers indicated in Table 3, polymers of the microgel structures were produced by the same method as in 2. Preparation of the Unsaturated Polyester Resin Example l-(2). All of the polymers obtained were in- The unsaturated polyester resins used in these Examsoluble in styrene. and were dispersed finely. ples were prepared by the same procedure as in Exam- The results of tests on the SMC and molded product ple 1, l) in accordance with the following recipe. are shown in Table 4.

Controls l l and 12 were also performed in the same Unsaturated polyester resin (UP3) way as in Examples 3 to 9 except as noted below. of Example l4 Maleic anhydride 1.75 mols Control l l lsophthalic acid (125 mol I Propylene glycol 205 mols In Examples 3 to 13, G -l was used instead of the mr- Acid value 42 Styrene 30% by weight Clngel polymer Unsaturated polyester resin [UP-4) Control 2 0f Example l5 3U Maleic anhydride 1.0 mol In Examples 3 to 13. 32 parts of the unsaturated poly- Phlhullc flnhydflde moi t (UP 2) was used instead of the micro el Pmpylene glycfl es er resm g Acid value 45 polymer. Styrene 30% by weight Table 3 Run Polymer Ruhhery Polymerizahle monomors (pans) Nos. having a substance (parts) microgel SlI'UClUH! COOH Types Poly- Styrene- Styrene Acrylo- Methyl Ethyl Acrylic Meth- (ontent hutadiene hutadiene nitrile methacrylate acid acrylic (wtfit l copolymer acrylate acid 3 2.0 6-] 2l l7 58 4 1 0-4 21 44 Q 32 3 5 2,) (1-5 l5 l8 2 5 (1 15 (3-6 It] Z4 3B 3 7 LI (1-7 h l5 77 2 8 1.8 (3-8 29 38 3 9 ll (1-9 15 4h 4 10 2.5 G-lll 2U 76 4 l l l.4 G-l l It) 69 I4 3 4 I] ll G42 Z0 63 I3 4 l3 l.3 G-l3 4U 35 23 2 Table 4 Modifying Solubility Stability Surface Adhesion polymer of the of SMC smoothness of paint Run modifying of the molded Nosv polymer in article "l styrene 3 SJ Insoluble Good Good I20 Good (finely dispersed] 4 6-4 Good Good [30 Good 5 G 5 Good Good I30 Good 6 (3-6 Good Good l-Nl Good 7 6-7 Good Good 1-45 Good 8 (3.3 Good Good 14H Good 9 6-9 Good Good 155 Good 10 G-IU Good Good iflll Fa r l l G-l l Good Good I45 Fair l2 G-IZ Good Good I Fair [3 G-l3 Good Good I30 Fair Control I l G'-l Fair Fair 280 Good Control l2 None Good Inferior 2200 Good alluu ed to stand [or Ill day; after its preparation Continued Unsaturated polyester resin (UP-) of Example lh Maleic anhydride l.() mol 2.2'-di(4-hydroxypropoxy" phenyl) propane l.() mol Acid value 46 Styrene by weight Unsaturated polyester resin (UP-6) of Example I? Maleic anhydride 0.3 mol Phthalie anhydride 0.2 mol lfi-Butanediol L02 mols Acid value 43 Styrene :ill /r' by weight Unsaturated polyester resin (UP-7) of Example lti Maleic anhydride it] moi Diethylene glycol LUZ mols Acid value 38 Styrene 32% by weight After allowing the resulting SMC to stand for l0 days, it was molded, and the properties of the molded article were measured. The results are shown in Table 5.

1 )Thu surface smoothness ul'u molded article obtained from SMC which has been allowed to stand for ll) days after its preparation.

EXAMPLE I9 I. Unsaturated Polyester Resin UP-l was used.

2. Polymer having a Microgel Structure Either 0-2 or G-l4 was used. G-l4 was a powdery polymer obtained by the method of Example 1, (2)

using 35 parts, as solids content, of a polybutadiene latex, parts ofstyrene, l parts of ion exchanged water. 30 parts of sodium dodecylbenzenesulfonate and 1.5 parts of potassium persulfate. G-l4 was not uniformly soluble in a monomer for curing an unsaturated polyester resin, such as styrene vinyl toluene or methyl methacrylate. l0 parts of G-l4 was mixed with parts of styrene. and the mixture was subjected to centrifugal separation at a speed of 7000 revolutions per minute for 20 minutes. The amount of the precipitated portion was about 90 by weight. G-l4 was neither soluble in UP-l.

3. Preparation of Soluble Polymer A carboxyl-containing polymer (S-l) having a molecular weight of about 50,000 was prepared from 97 parts of methyl methacrylate and 3 parts of acrylic acid. 5-] was soluble in styrene, methyl methacrylate, and vinyl toluene. and had a carboxyl content of 1.8 by weight.

4. Preparation of Sheet Molding Compound (SMC) SMC was prepared in accordance with the following recipe.

(parts) (parts) Unsaturated polyester resin (UPl 58 58 Microgel polymer 0-2 0-14 (7) (7) Soluble polymer (S-i 5 S Styrene 3t) 3t) Zinc stearate 4 4 t-Butyl perbenloate L5 L5 t-Butyl catechol (I114 0.04 Magnesium oxide l2 L2 Calcium carbonate i It) it) Chopped strand of glass fibers (fiber length 2 inches) '45 The SMC so produced was stable during storage for 3 months, and its surface did not become tacky. The resulting SMC was stored at room temperature for 5 days. 10 days. 20 days and 30 days after its preparation. and molded at a temperature of 140C. and a pressure of ZOOkg/cm with a molding cycle of 3 minutes. The properties of the molded articles are given in Table 6.

In order to clarify the superior advantages of this invention. some control examples were performed. In each of the controls; the procedure of Example [9 was followed except as noted below.

Control I3 42 parts of UP-l (the total amount UP-l was parts) was used instead of 7 parts of 0-2. 5 parts of 8-1 and 30 parts of styrene in Example 19, No. l, (4).

Control 14 Instead of 7 parts of (3-2 in Example 19, No. l, (4). 7 parts of S-l was used (the total amount of S-l was 12 parts).

Control 15 In Example l9, No. 2. (4). 5 parts of 6-14 was used instead of 5 parts of 5-1 (the total amount of G- l 4 was 12 parts).

For reference. the viscosity of a resin composition containing no thickner and glass fibers was measured during the production of SMC. The impregnatability of the resin composition in the glass fibers at the time of producing SMC was observed, and the results shown in Table 6 were obtained.

Generally when the viscosity of the resin composition before addition of a thickner is too high. the impregnatability of the resin composition is poor. In Control 15, the viscosity of the resin composition is poor. However. in the case of No. 2 containing G-l4 and S-l and No. 1 containing (3-2 and 8-1. the viscosity was unexpectedly low. and the impregnatability was good.

Table 6 i y lCOOH T Jiccosil y lmpreg- Surface Flexu- Overllflodtf rcontent Solubiof the inatobiq y ],,3 smoothness 01" fill all l uns; illlfl lof the lity of composi ion! lity molded strenevalu- RGOL'. polymer modifying the cori ainini in glass articles gth of ration: 1 [polymer l polymer ihicimer fibers Timber of days the i l K y i and glass of storage 01' molded fibers SMC ar- 'tcl s 9o l o (k /mm lc a... .L l l ZOO lair ood Good Good 1 L 'oorl "ood k l l l p 1Y0 1: 0 zoo zo 1 i l Finelyll portly .ZQPUF- d if ix ure- 5 Good "Coocl CB6 ood Q nl lT-l (iii M1 5";0 Foil" flood (200d 300d 00d .-.,...m l: 29. 'oi m] Good 'Trood Tn- Inl, 1 lone J 1H0 llI Good Good to .Eg- OOT r1' r1- OI 01 l 2500 2 l 2500 l r'iomwl Good Fair e Fair Poor 1 I 7 l l l 1.: soluble #00 Fair 200 570 500 800 1 Poor 1 i or or P r T i miiiol Insoluble In- Good Good Good Good E l Q I l 1 l (timely Q00 fEllOI 00d 200 200 200 200 1 Poor 4 d1 :persed) i l l EXAMPLES TO 43 These Examples will illustrate the effects of various modifying polymer mixtures on the unsaturated polyester resin.

1. Unsaturated Polyester Resin UP-2 was used.

2. Modifying Polymer A mixture of each of the soluble polymers shown in Table 8 and a microgel polymer produced from each of the rubbery substances and polymerizable monomers shown in Table 7 was used.

3. Preparation of Sheet Molding Compound (SMC) A sheet molding compound was prepared in accordance with the following recipe. and molded in the same way as in Example 1.

The results of tests on the SMC and molded articles are shown in Table 9.

Controls l6 and 17 were performed in accordance with Examples 20 to 43 except as noted below.

Control 16 Unsaturated polyester resin (UP-2) 65 parts Modifyin polymer mixture l2 Styrene g 23 Control 17 Zinc Stearate 4 l-Butyl perbenzoate 1.5 glfiz 'l g gfa' 's 3' in Example 36. 6.5 parts of 8-4 (the total amount of Magnesium oxide LB 5-4 was 12 parts) was used instead of 6.5 parts of 6-22. chwped M The stability of SMC was poor. and the polymeric ma- (fihcr length 1 Inch) terial excuded onto its surface to make it tacky.

Table 7 Polymers Ruhhery Polymerizable monomers (parts) having a substance Sty- Methyl Ethyl Acrylo- Divinyl Acrylic Meth' COOH microgel {parts} rene methacryacrynitrile benzene acid acrylic content structure Poly- Styrene late late acid (\vtfk l hutahut-adidiene cne copolymer (J-IS l5 26 5h 3 1.9 (i-lti 30 5i] l5 5 11) (i-l7 l0 I5 411 I 3 1,4 (H8 5 In 7. .8 0.2 3 1.8 (i-ll 40 Ill 37 3 IX (i-Zll I5 25 oil 0 [L2] 30 5U Zll 0 (1-2] Ill I5 45 25 0 (3-23 5 Ill 74.8 (l."' 0 (1-24 40 Ill 4U (l of paint ll lolll Meth- Monomethyl COOH acrylic ester of content acid maleic 1.9? l

acid

Solubility Surface of SMC after smoothness Adhesion 10 days of molded storage articles Table 8 Composition of polymers (parts) Styrene Methyl Ethyl Ethy- Vinyl Vinyl Acrylic meth acrylene chloacetate acid acrylate ride late Table 9 Modifying polymers COOH lmpreg- Emmples Soluble polymers Microgel content natahi Ty pes Amount polymers of modilily in (parts) Types Amount fying glass (parts) polymer (92) fibers Soluble poly mers Fair 445 6666655 56h7fih87868b12 2341.5867 134599945 SSSSSSSSSSSSSSSSSSSSSSSS ill 43 Control lh Control l7 Fair 600 EXAMPLE 44 45 -Continued 1. Preparation of Modifying Polymer Mixture gggl z ggfxf 3,13 A glass reaction vessel equipped with a stirrer, a gas raglriesium oxide U (1)1) flow inlet tube. a condenser and a thermometer was 2262 smmd of glass fibers ent. of a latex of a (fiber length l inch) 95 53 parts of methyl 3.5 parts of acrylic A sheet molding compound was prepared in accordance with the above recipe. It was stable during stor- 2.0 parts of sodium dodecyl benzenesulage for 3 months, and its surface did not become tacky.

lfate. With good 55 The impregnatability of it in glass fibers was good. mixing, the reaction was performed for 6 hours in an When the SMC was molded in the same way as in Exatmosphere of nitrogen at C. The resulting emulsion ample 19. the surface of the molded article was good, and it did not adhere to the mold to cause the loss of the surface luster of the molded article.

yrene using a centrifugal separator 60 ymer was a mixture of about 50 7c EXAMPLES 45 TO 54 charged with 30 parts, as solids cont copolymer of styrene and butadiene.

methacrylate, 13.5 parts of styrene,

acid. I parts of ion exchanged water, 0.6 part of lauryl mercaptan fonate and 0.4 part of potassium persu was salted out. washed and dried to obtain a powdery polymeric material (M- l The test on the solubility of the polymer in st showed that this pol 3. Preparation of SMC A sheet molding compound was prepared in accordance with the following recipe.

cured unsaturated polyester resins. the composition comprising l. 60 to 97 by weight of an unsaturated polyester resin which is a liquid mixture of at least one unsat- Unsaturated polyester resin 63 parts 5 urated polyester selected from the group consisting Microgel polymer 6 f Soluhlc pmymer h the unsaturated polyesters from unsaturated direne 22 basic carboxylic acid and the anhydride and dia zt g f g g L me thylesters thereof. ethylene oxide. propylene p-Berwuquinone (it l0 oxide or from said unsaturated dibasic carboxylic 5 acid together with saturated dicarboxylic acid and Chopped Smmd f gm fib said diol and at least one vinyl monomer for curing (fiber length l inch) lllt) [he polyester and 2. 40 to 3 by weight ofa combined modifying poly- 4. Unsaturated Polyester Resin 5 mer component which comprises UP-2 (Examples 45 and 50). UP-4 (Examples 46 and a. 80 to 5 by weight ofa polymer of the microgel 5] UP-5 (Examples 47 and 52). UP-() (Examples 48 structure which is obtained by polymerizing 97 to and 53 and UP-7 (Examples 49 and 54) were used. 30 by weight of at least one radical polymeriz- The results are shown in Table 10 below. able monomer in the presence of 3 to 70 70 by Table 10 Unsatu- Modifying COOH lmpreg- Stahility Surface smoothness Adhesion Examples rated polymers content of natahiliof SMC of molded articles of polyester the modifyty in (i Period of storage paint resin ing polymer glass (wt/ii) fibers 5 days l0 days 21) days 45 UP-Z G- l 5 L9 Fair Good Good Good Good Good 8-5 120 I I50 46 UP-4 (3-15 1.9 Good Good Good 5-5 I60 I60 200 47 UP-S (3-15 L9 Good Good Good S-S I20 I 150 48 UP-o G l 5 l .9 Good Good Good 5-5 140 140 200 49 UP-7 Ci-l5 l.9 Good Good Good S5 130 1-30 160 50 UP-2 G-2ll [.3 Good Good Good 5-7 120 I20 I30 5l UP 4 G 'll) 1.3 Good Good Good 8-? iso 1x0 200 52 UP5 G-Zll L3 Good Good Good 8-7 130 I30 I80 53 UP-6 0-20 1.3 Good Good Good 5.7 no I I 54 UP-7 G-Zll L3 Good Good Good What we claim is: weight of at least one rubbery polymer having 1 A d t t d l t double bonds in the molecule. and is finely disn F i hunsa a 2'. p0 t if g 5 persible, without dissolving. in both of said unsatnon u m t S uc e ar O urated polyester resin and said unsaturated cure unsaturate p0 yester resins. e compost ion monomer for curing the polyester and Compnsmg b. 20 to 95 by weight of at least one thermoplasto 97 F of a uncu rcd unsaturated tic polymer soluble in at least one of said unsatupolyester resin which is a liquid mixture of at least 50 rated polyester resin and said unsaturated mono one unsaturated polyester selected from the group mer for curing tha polyester conslsung 9 h unsaturaled Polyesters from at least one of polymers (a) and (b) containing carsaturated dibasic carboxylic acid and the anhydride boxy] groups being 01 to 10 by weight based on the 'eg 95 tm a g mi weight of oi mas (a) and (b). l "ii e or J ii 1 a if 55 3. The composition of claim 1 wherein said modifyy q er m um e oxy am ing polymer of the microgel structure further contains and said diol and at least one vinyl monomer for at least one kind of polar group other than a carboxyl curing the polyester. and u in the m I cule 2. 40 to 3 by weight Ofa modifying polymer of the 5; F. l 2 h H t e of microgel structure which is obtained by polymeriz- 6U e Folnposmon 0 C gas t ing. 97 to 30 by weight of at least one vinyl polymersm) an er con monomer in the presence 0f 3 to 70 by weight least one kind of polar group other than a car oxy of at least one rubbery polymer having carbon to group m the molfflfulfi I carbon double bonds in the molecule. is finely dis- The COmPQSmOQ 0f Cllllm l Whefeln Said ypersible. without dissolving. in both of said unsatu' g p ym r f h microgel tructure is a polymer 0 rated polyester resin and said unsaturated monomer for curing the polyester. and contains O.l to 10 by weight of carboxyl groups in the molecule. 2. An uncured unsaturated polyester resin composition useful in the production of molded articles of tained by copolymerizing an unsaturated carboxylic acid with at least one of styrene. methyl methacrylate and acrylonitrile in the presence of polybutadiene or polyisoprene. 

1. AN UNCURED UNSATURATED POLYESTER RESIN COMPOSITION USEFUL IN THE PRODUCTION OF MOLDED ARTICLES OF CURED UNSATURATED POLYESTER RESIN, THE COMPOSITION COMPRISING
 1. 60 TO 97% BY WEIGHT OF AN UNCURED UNSATURATED POLYESTER RESIN WHICH IS A LIQUID MIXTURE OF AT LEAST ONE UNSATURATED POLYESTER SELECTED FROM THE GROUP CONSISTING OF THE UNSATURATED POLYESTERS FROM UNSATURATED DIBASIC CARBOXYLIC ACID AND THE ANHYDRIDE AND DIMETHYLESTERS THEREOF, ETHYLENE OXIDE, PROPYLENE OXIDE OR FROM SAID UNSATURATED DIBASIC CARBOXYLIC ACID TOGETHER WITH SATURATED DICARBOXYLIC ACID AND SAID DIOL AND AT LEAST ONE VINYL MONOMER FOR CURING THE POLYESTER, AND
 2. 40 TO 3% BY WEIGHT OF A MODIFYING POLYMER OF THE MICROGEL STRUCTURE WHICH IS OBTAINED BY POLYMERIZING, 97 TO 30 % BY WEIGHT OF AT LEAST ONE VINYL MONOMER IN THE PRESENCE OF 3 TO 70% BY WEIGHT OF AT LEAST ONE RUBBERY POLYMER HAVING CARBON TO CARBON DOUBLE BONDS IN THE MOLECULE, IS FINELY DISPERSIBLE, WITHOUT DISSOLVING, IN BOTH OF SAID UNSATURATED POLYESTER RESIN AND SAID UNSATURATED MONOMER FOR CURING THE POLYESTER, AND CONTAINS 0.1 TO 10% BY WEIGHT OF CARBOXYL GROUPS IN THE MOLECULE.
 2. 40 to 3 % by weight of a modifying polymer of the microgel structure which is obtained by polymerizing, 97 to 30 % by weight of at least one vinyl monomer in the presence of 3 to 70 % by weight of at least one rubbery polymer having carbon to carbon double bonds in the molecule, is finely dispersible, without dissolving, in both of said unsaturated polyester resin and said unsaturated monomer for curing the polyester, and contains 0.1 to 10 % by weight of carboxyl groups in the molecule.
 2. An uncured unsaturated polyester resin composition useful in the production of molded articles of cured unsaturated polyester resins, the composition comprising
 2. 40 to 3 % by weight of a combined modifying polymer component which comprises a. 80 to 5 % by weight of a polymer of the microgel structure which is obtained by polymerizing 97 to 30 % by weight of at least one radical polymerizable monomer in the presence of 3 to 70 % by weight of at least one rubbery polymer having double bonds in the molecule, and is finely dispersible, without dissolving, in both of said unsaturated polyester resin and said unsaturated monomer for curing the polyester, and b. 20 to 95 % by weight of at least one thermoplastic polymer soluble in at least one of said unsaturated polyester resin and said unsaturated monomer for curing the polyester, at least one of polymers (a) and (b) containing carboxyl groups being 0.1 to 10 % by weight based on the total weight of polymers (a) and (b).
 3. The composition of claim 1 wherein said modifying polymer of the microgel structure further contains at least one kind of polar group other than a carboxyl group in the molecule.
 4. The composition of claim 2 wherein at least one of said modifying polymers (a) and (b) further contains at least one kind of polar group other than a carboxyl group in the molecule.
 5. The composition of claim 1 wherein said modifying polymer of the microgel structure is a polymer obtained by copolymerizing an unsaturated carboxylic acid with at least one of styrene, methyl methacrylate and acrylonitrile in the presence of polybutadiene or polyisoprene. 